Q:

Program to delete a new node from the beginning of the doubly linked list

belongs to collection: Doubly Linked List Programs

robaa
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2022-11-10
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Explanation

In this program, we will create a doubly linked list and delete a node from the beginning of the list. If the list is empty, print the message "List is empty". If the list is not empty, we will make the head to point to next node in the list then; we will delete the first node.

Consider the above example, new was the head of the list. Make head to point to next node in the list. Now, node 1 will become the new head of the list thus, deleting node new.

Algorithm

  1. Define a Node class which represents a node in the list. It will have three properties: data, previous which will point to the previous node and next which will point to the next node.
  2. Define another class for creating a doubly linked list, and it has two nodes: head and tail. Initially, head and tail will point to null.
  3. deleteFromStart() will delete a node from the beginning of the list:
    1. It first checks whether the head is null (empty list) then, it will return from the function as there is no node present in the list.
    2. If the list is not empty, it will check whether the list has only one node.
    3. If the list has only one node, it will set both head and tail to null.
    4. If the list has more than one node then, the head will point to next node in the list and delete the old head node.
  4. display() will show all the nodes present in the list.
    1. Define a new node 'current' that will point to the head.
    2. Print current.data till current points to null.
    3. Current will point to the next node in the list in each iteration.

Input:

 

#Add nodes to the list  

dList.addNode(1);  

dList.addNode(2);  

dList.addNode(3);  

dList.addNode(4);  

dList.addNode(5);   

Output:

Original List: 1 2 3 4 5 
Updated List: 2 3 4 5 
Updated List: 3 4 5 
Updated List: 4 5 
Updated List: 5 
Updated List: List is empty
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All Answers

robaa
2022-11-10
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Python

#Represent a node of doubly linked list  
class Node:  
    def __init__(self,data):  
        self.data = data;  
        self.previous = None;  
        self.next = None;  
          
class DeleteStart:  
    #Represent the head and tail of the doubly linked list  
    def __init__(self):  
        self.head = None;  
        self.tail = None;  
          
    #addNode() will add a node to the list  
    def addNode(self, data):  
        #Create a new node  
        newNode = Node(data);  
          
        #If list is empty  
        if(self.head == None):  
            #Both head and tail will point to newNode  
            self.head = self.tail = newNode;  
            #head's previous will point to None  
            self.head.previous = None;  
            #tail's next will point to None, as it is the last node of the list  
            self.tail.next = None;  
        else:  
            #newNode will be added after tail such that tail's next will point to newNode  
            self.tail.next = newNode;  
            #newNode's previous will point to tail  
            newNode.previous = self.tail;  
            #newNode will become new tail  
            self.tail = newNode;  
            #As it is last node, tail's next will point to None  
            self.tail.next = None;  
              
    #deleteFromStart() will delete a node from the beginning of the list  
    def deleteFromStart(self):  
        #Checks whether list is empty  
        if(self.head == None):  
            return;  
        else:  
            #Checks whether the list contains only one element  
            if(self.head != self.tail):  
                #head will point to next node in the list  
                self.head = self.head.next;  
                #Previous node to current head will be made None  
                self.head.previous = None;  
                  
            #If the list contains only one element   
            #then, it will remove the node, and now both head and tail will point to None  
  
            else:  
                self.head = self.tail = None;  
                  
    #display() will print out the nodes of the list  
    def display(self):  
        #Node current will point to head  
        current = self.head;  
        if(self.head == None):  
            print("List is empty");  
            return;  
        while(current != None):  
            #Prints each node by incrementing pointer.  
            print(current.data),  
            current = current.next;  
        print();  
         
dList = DeleteStart();  
#Add nodes to the list  
dList.addNode(1);  
dList.addNode(2);  
dList.addNode(3);  
dList.addNode(4);  
dList.addNode(5);  
   
#Printing original list  
print("Original List: ");  
dList.display();  
while(dList.head != None):  
    dList.deleteFromStart();  
    #Printing updated list  
    print("Updated List: ");  
    dList.display();

 

Output:

Original List: 
1 2 3 4 5 
Updated List: 
2 3 4 5 
Updated List: 
3 4 5 
Updated List: 
4 5 
Updated List: 
5 
Updated List: 
List is empty

 

C

#include <stdio.h>  
   
//Represent a node of the doubly linked list  
  
struct node{  
    int data;  
    struct node *previous;  
    struct node *next;  
};      
   
//Represent the head and tail of the doubly linked list  
struct node *head, *tail = NULL;  
   
//addNode() will add a node to the list  
void addNode(int data) {  
    //Create a new node  
    struct node *newNode = (struct node*)malloc(sizeof(struct node));  
    newNode->data = data;  
      
    //If list is empty  
    if(head == NULL) {  
        //Both head and tail will point to newNode  
        head = tail = newNode;  
        //head's previous will point to NULL  
        head->previous = NULL;  
        //tail's next will point to NULL, as it is the last node of the list  
        tail->next = NULL;  
    }  
    else {  
        //newNode will be added after tail such that tail's next will point to newNode  
        tail->next = newNode;  
        //newNode's previous will point to tail  
        newNode->previous = tail;  
        //newNode will become new tail  
        tail = newNode;  
        //As it is last node, tail's next will point to NULL  
        tail->next = NULL;  
    }  
}  
   
//deleteFromStart() will delete a node from the beginning of the list  
void deleteFromStart() {  
    //Checks whether list is empty  
    if(head == NULL) {  
        return;  
    }  
    else {  
        //Checks whether the list contains only one element  
        if(head != tail) {  
            //head will point to next node in the list  
            head = head->next;  
            //Previous node to current head will be made NULL  
            head->previous = NULL;  
        }  
        //If the list contains only one element   
        //then, it will remove node and now both head and tail will point to NULL  
        else {  
            head = tail = NULL;  
        }  
    }  
}  
   
//display() will print out the nodes of the list  
void display() {  
    //Node current will point to head  
    struct node *current = head;  
    if(head == NULL) {  
        printf("List is empty\n");  
        return;  
    }  
    while(current != NULL) {  
        //Prints each node by incrementing pointer.  
        printf("%d ",current->data);  
        current = current->next;  
    }  
    printf("\n");  
}  
      
int main()  
{  
    //Add nodes to the list  
    addNode(1);  
    addNode(2);  
    addNode(3);  
    addNode(4);  
    addNode(5);  
      
    //Printing original list  
    printf("Original List: \n");  
    display();  
    while(head != NULL) {  
        deleteFromStart();  
        //Printing updated list  
        printf("Updated List: \n");  
        display();  
    }      
   
    return 0;  
}

 

Output:

Original List: 
1 2 3 4 5 
Updated List: 
2 3 4 5 
Updated List: 
3 4 5 
Updated List: 
4 5 
Updated List: 
5 
Updated List: 
List is empty

 

JAVA

public class DeleteStart {  
      
    //Represent a node of the doubly linked list  
  
    class Node{  
        int data;  
        Node previous;  
        Node next;  
          
        public Node(int data) {  
            this.data = data;  
        }  
    }  
      
    //Represent the head and tail of the doubly linked list  
    Node head, tail = null;  
      
    //addNode() will add a node to the list  
    public void addNode(int data) {  
        //Create a new node  
        Node newNode = new Node(data);  
          
        //If list is empty  
        if(head == null) {  
            //Both head and tail will point to newNode  
            head = tail = newNode;  
            //head's previous will point to null  
            head.previous = null;  
            //tail's next will point to null, as it is the last node of the list  
            tail.next = null;  
        }  
        else {  
            //newNode will be added after tail such that tail's next will point to newNode  
            tail.next = newNode;  
            //newNode's previous will point to tail  
            newNode.previous = tail;  
            //newNode will become new tail  
            tail = newNode;  
            //As it is last node, tail's next will point to null  
            tail.next = null;  
        }  
    }  
      
    //deleteFromStart() will delete a node from the beginning of the list  
    public void deleteFromStart() {  
        //Checks whether list is empty  
        if(head == null) {  
            return;  
        }  
        else {  
            //Checks whether the list contains only one element  
            if(head != tail) {  
                //head will point to next node in the list  
                head = head.next;  
                //Previous node to current head will be made null  
                head.previous = null;  
            }  
            //If the list contains only one element   
            //then, it will remove node and now both head and tail will point to null  
            else {  
                head = tail = null;  
            }  
        }  
    }  
      
    //display() will print out the nodes of the list  
    public void display() {  
        //Node current will point to head  
        Node current = head;  
        if(head == null) {  
            System.out.println("List is empty");  
            return;  
        }  
        while(current != null) {  
            //Prints each node by incrementing the pointer.  
  
            System.out.print(current.data + " ");  
            current = current.next;  
        }  
        System.out.println();  
    }  
      
    public static void main(String[] args) {  
          
        DeleteStart dList = new DeleteStart();  
        //Add nodes to the list  
        dList.addNode(1);  
        dList.addNode(2);  
        dList.addNode(3);  
        dList.addNode(4);  
        dList.addNode(5);  
          
        //Printing original list  
        System.out.println("Original List: ");  
        dList.display();  
        while(dList.head != null) {  
            dList.deleteFromStart();  
            //Printing updated list  
            System.out.println("Updated List: ");  
            dList.display();  
        }  
    }  
}

 

Output:

Original List: 
1 2 3 4 5 
Updated List: 
2 3 4 5 
Updated List: 
3 4 5 
Updated List: 
4 5 
Updated List: 
5 
Updated List: 
List is empty

 

C#

 using System;   
namespace DoublyLinkedList   
{                       
    public class Program  
    {  
        //Represent a node of the doubly linked list  
  
        public class Node<T>{  
            public T data;  
            public Node<T> previous;  
            public Node<T> next;  
              
            public Node(T value) {  
                data = value;  
            }  
        }  
          
        public class DeleteStart<T>{  
            //Represent the head and tail of the doubly linked list  
            public Node<T> head = null;               
             public Node<T> tail = null;  
              
            //addNode() will add a node to the list  
            public void addNode(T data) {  
                //Create a new node  
                Node<T> newNode = new Node<T>(data);  
   
                //If list is empty  
                if(head == null) {  
                    //Both head and tail will point to newNode  
                    head = tail = newNode;  
                    //head's previous will point to null  
                    head.previous = null;  
                    //tail's next will point to null, as it is the last node of the list  
                    tail.next = null;  
                }  
                else {  
                    //newNode will be added after tail such that tail's next will point to newNode  
                    tail.next = newNode;  
                    //newNode's previous will point to tail  
                    newNode.previous = tail;  
                    //newNode will become new tail  
                    tail = newNode;  
                    //As it is last node, tail's next will point to null  
                    tail.next = null;  
                }  
            }  
      
            //deleteFromStart() will delete a node from the beginning of the list  
            public void deleteFromStart() {  
                //Checks whether list is empty  
                if(head == null) {  
                    return;  
                }  
                else {  
                    //Checks whether the list contains only one element  
                    if(head != tail) {  
                        //head will point to next node in the list  
                        head = head.next;  
                        //Previous node to current head will be made null  
                        head.previous = null;  
                    }  
                    //If the list contains only one element   
                    //then, it will remove node and now both head and tail will point to null  
                    else {  
                        head = tail = null;  
                    }  
                }  
            }  
      
            //display() will print out the nodes of the list  
            public void display() {  
                //Node current will point to head  
                Node<T> current = head;  
                if(head == null) {  
                    Console.WriteLine("List is empty");  
                    return;  
                }  
                while(current != null) {  
                    //Prints each node by incrementing the pointer.  
  
                    Console.Write(current.data + " ");  
                    current = current.next;  
                }  
                Console.WriteLine();  
            }  
        }  
          
        public static void Main()  
        {  
            DeleteStart<int> dList = new DeleteStart<int>();  
            //Add nodes to the list  
            dList.addNode(1);  
            dList.addNode(2);  
            dList.addNode(3);  
            dList.addNode(4);  
            dList.addNode(5);  
   
            //Printing original list  
            Console.WriteLine("Original List: ");  
            dList.display();  
            while(dList.head != null) {  
                dList.deleteFromStart();  
                //Printing updated list  
                Console.WriteLine("Updated List: ");  
                dList.display();  
            }  
        }      
    }  
}

 

Output:

Original List: 
1 2 3 4 5 
Updated List: 
2 3 4 5 
Updated List: 
3 4 5 
Updated List: 
4 5 
Updated List: 
5 
Updated List: 
List is empty

 

PHP

<!DOCTYPE html>  
<html>  
<body>  
<?php  
//Represent a node of doubly linked list  
class Node{  
    public $data;  
    public $previous;  
    public $next;  
      
    function __construct($data){  
        $this->data = $data;  
    }  
}  
class DeleteStart{  
    //Represent the head and tail of the doubly linked list  
    public $head;  
    public $tail;  
    function __construct(){  
        $this->head = NULL;  
        $this->tail = NULL;  
    }  
      
    //addNode() will add a node to the list  
    function addNode($data) {  
        //Create a new node  
        $newNode = new Node($data);  
          
        //If list is empty  
        if($this->head == NULL) {  
            //Both head and tail will point to newNode  
            $this->head = $this->tail = $newNode;  
            //head's previous will point to NULL  
            $this->head->previous = NULL;  
            //tail's next will point to NULL, as it is the last node of the list  
            $this->tail->next = NULL;  
        }  
        else {  
            //newNode will be added after tail such that tail's next will point to newNode  
            $this->tail->next = $newNode;  
            //newNode's previous will point to tail  
            $newNode->previous = $this->tail;  
            //newNode will become new tail  
            $this->tail = $newNode;  
            //As it is last node, tail's next will point to NULL  
            $this->tail->next = NULL;  
        }  
    }  
      
    //deleteFromStart() will delete a node from the beginning of the list  
    function deleteFromStart() {  
        //Checks whether list is empty  
        if($this->head == NULL) {  
            return;  
        }  
        else {  
            //Checks whether the list contains only one element  
            if($this->head != $this->tail) {  
                //head will point to next node in the list  
                $this->head = $this->head->next;  
                //Previous node to current head will be made NULL  
                $this->head->previous = NULL;  
            }  
            //If the list contains only one element   
            //then, it will remove node and now both head and tail will point to NULL  
            else {  
                $this->head = $this->tail = NULL;  
            }  
        }  
    }  
      
    //display() will print out the nodes of the list  
    function display() {  
        //Node current will point to head  
        $current = $this->head;  
        if($this->head == NULL) {  
            print("List is empty <br>");  
            return;  
        }  
        while($current != NULL) {  
            //Prints each node by incrementing pointer.  
            print($current->data . " ");  
            $current = $current->next;  
        }  
        print("<br>");  
    }  
}  
      
$dList = new DeleteStart();  
//Add nodes to the list  
$dList->addNode(1);  
$dList->addNode(2);  
$dList->addNode(3);  
$dList->addNode(4);  
$dList->addNode(5);  
   
//Printing original list  
print("Original List: <br>");  
$dList->display();  
while($dList->head != NULL) {  
    $dList->deleteFromStart();  
    //Printing updated list  
    print("Updated List: <br>");  
    $dList->display();  
}  
?>  
</body>  
</html>

 

Output:

Original List: 
1 2 3 4 5 
Updated List: 
2 3 4 5 
Updated List: 
3 4 5 
Updated List: 
4 5 
Updated List: 
5 
Updated List: 
List is empty

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Doubly Linked List Programs
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